Analysis Of Optical Performance On Organic Solar Cell Based On Transfer Matrix Method

Organic solar cells(OSC) are attracting increasing attention because of their light weight,low cost, fabrication at low temperature, mechanical flexibility and low environmental-loadwhen compared to inorganic silicon solar cells. Over the past years, increasing the lightabsorption efficiency in the active layer has been considered to be a key factor to improve thepower conversion efficiency of the OSC device. But currently, most studies have focused onthe synthesis of new materials while the use of physical mechanisms, such as interferenceprinciple, microcavity effect to improve the light absorption are rarely reported. At the sametime, improving the light absorption is also an essential factor to improve the externalquantum efficiency of the device.The thickness of thin film in organic solar cells was normally less than the wavelength ofincident light, so the absorption in these thin film multilayer structures typically exhibitsstrong interference due to multiple reflection and transmission at the interfaces. Thus, theactive layer absorption efficiency is functions of the optical properties of the materialsemployed, excitation wavelength, layer thicknesses, and the layer configuration. Fortunately,the interference can be modeled with simple and accurate methods, which could yield reliableinformation about the relationship between total optical absorption and the influence factorsof it. The optical transfer-matrix theory, a powerful optical modeling tool, has been widelyapplied to simulate optical absorption and predict related electrical performance.First of all, optical simulations based on transfer matrix method, combined with asoftware MATLAB have been performed to investigate the optical properties of a invertedpolymer solar cell (IPSC). The effects of thickness, angle of incidence and structure on theoptical performance of IPSC are studied theoretically. Simulations reveal that excitationwavelength, layer thicknesses, and the layer configuration all have a certain degree of impacton the active layer absorption efficiency.Then the effects of electrodes on the optical performance of bilayer heterojunctionorganic solar cells have been investigated when microcavity structure is introduced into it. Itturns out that the absorption of active layer is mainly influenced by phase shift of thereflection of top electrode but not the transmittivity of it. Furthermore, simulationsdemonstrate that both reflectivity and reflection phase shift of back electrode play importantroles in active layer optical absorption when one-dimensional photon-crystals(1DPCs)composed of positive and negative refractive index materials is introduced into bilayerheterojunction organic solar cells. At last, we design and analyse an organic solar cell structure based on Si Substrat(SOSC). The effects of active layer thickness, capping layer thickness and transport layerthickness on the optical absorption of active layer have been deeply investigated. The resultsshow that the SOSC, which Si/SiO2/Ag as the back electrode, a transparent Ag metal thin filmwhich is overcoated with a refractive index matching layer as the incident electrode, canreplace the traditional OSC which Glass/ITO as the incident electrod and its active layerthickness could be optimized by the microcavity effect. The active layer optical absorptioncan be increased to a certain extent by adjusting the thickness of refractive index matchinglayer and the transport layer.The research of optical properties of organic solar cell provides a theoretical basis to itsfuture structural design and the improvement of the energy conversion efficiency.